Cardiac arrhythmia, a frequent problem in many patients, particularly those suffering from myocardial infarction, as well as anesthetized patients and patients under treatment with digitalis, a cardiac tonic, is a variation from the normal rhythm of the heart beat and includes sinus arrhythmia, premature beat, heart block, atrial fibrillation, atrial flutter, pulsus alternans, and paroxysmal tachycardia. Cardiac contractions (heart beats) are initiated by electrical impulses originating in the sinoatrial node of the heart at regular intervals, generally about 60-100 beats per minute. The impulses rapidly spread by conduction to all parts of the ventricles stimulating synchronous contractions of all ventricular muscle. Arrhythmias occur as a result of any abnormality in this rhythmic process, for example, in the site of origin of the impulse, its regularity, strength, and its conduction. An excellent discussion of the mechanisms involved, including the sodium, potassium, and calcium channeling effects which occur, and the cardiac effects of current medications, particularly sodium channel-blocking drugs such as quinidine, procainamide, and lidocaine is provided by Luc M. Hondeghem and Jay W. Mason in Chapter 13, "Agents Used In Cardiac Arrhythmias" of the Lange Medical Book, Basic and ClinicaI Pharmacology, Third Edition, Edited by Bertram G. Katzung, Appleton and Lange, Norwalk, Conn./Los Altos, Calif., page 151.
U.S. Pat. No. 4,581,370 describes certain imidazolium salts which are useful as antiarrhythmic agents. U.S. Pat. No. 4,804,662 describes 4-[1H-imidazol-1-yl] benzamides and their use in the treatment of cardiac arrhythmias. However, these patents do not suggest the pharmaceutical compositions of the present invention comprising a compound having a nitrogen containing group connected via an ethanediylidene group to an imino group.